A device for making a spun fleece for making nonwoven mats is known comprising a spinning nozzle or spinneret system, a cooling shaft, a stretching gap, a diffuser shaft, a continuously moving fleece receiving conveyor and a device for feeding process air and for pulling outflowing air through the fleece delivery conveyor. The cooling shaft having a shaft wall is provided with a plurality of air orifices and process air required for cooling is introducible through the air orifices to provide an air flow. The air flow is at least partially drawn through the fleece receiving conveyor.
With the known device for making a spun fleece the deposited lengths of endless filament loops which substantially determine the quality of the manufactured spun fleece depend upon the flow rate of thermoplastic material which forms the endless filaments, according to the flow rate of the process air and according to the flow rate of outflowing air, the geometry of the device for making a spun fleece and other parameters. If one keeps the described parameters constant, the deposited lengths of the endless filament loops cannot be changed with ease. Particularly the loop lengths cannot be altered because of changes in the spun fleece width. If one changes the given parameters to adjust the deposited lengths, complex not easily reproducible structures result.